Protective clothing refers to primary and secondary protective clothing (per ASTM Standard F1494-03). Primary protective clothing is designed to be worn for work activities during which significant exposure to molten substance splash, radiant heat, arc flash, and/or flame is likely to occur. Secondary protective clothing, on the other hand, is protective clothing designed for continuous wear for work activities in designated locations in which intermittent exposure to molten substance splash, radiant heat, arc flash, and/or flame source is possible.
Protective clothing in the work place is important because it is the employer's responsibility to identify risks and hazards in the workplace and seek out appropriate protective garments and equipment for the protection of workers. Common workplace hazards include, for example: open flames, high heat, flash fire, flammable liquids, flammable soils, molten metals, sparks, slag from flame cutting, welding, high voltage electrical discharges, electric arc events, vapors from volatile liquids, and combustible dusts. These hazards may be encountered at structural fires, active military fields, Wildland fires, urban search and rescue incidents, in foundries, at electrical utilities, in the chemical, oil, gas and petrochemical industries, in auto racing, areas of rioting, and illicit drug manufacturing labs, just to mention a few.
Fabrics have been developed for use in protective clothing. Popular fabrics include: PBI GOLD® (PBI Performance Products, Inc of Charlotte, N.C.), COMFORT BLEND® (Tencate of Union City, Ga.), FREESTYLE™ (Tencate of Union City, Ga.), and INDURA® ULTRASOFT® (Westex, Inc. of Chicago, Ill.). PBI GOLD® is a 40% PBI/60% para-aramid blend. COMFORT BLEND® is 65% meta-aramid/35% FR rayon blend. FREESTYLE™ is 93% meta-aramid/5% para-aramid (KEVLAR®) fiber/2% antistatic fiber. INDURA® ULTRASOFT® is 88% FR cotton/12% nylon blend (all % are by weight of the fabric). Each of these fabrics has its own unique blend of properties.
The present invention provides a fiber blend, or yarn from said fiber blend, from which a fabric for a protective garment may be constructed. The blend includes a lyocell fiber and a flame resistant fiber, also known as an “FR” fiber. None of the flame resistant fabrics described above include lyocell fibers.
Lyocell is a flammable fiber made from wood pulp cellulose. The Federal Trade Commission defines lyocell as “a cellulose fabric that is obtained by an organic solvent spinning process.” The FTC classifies the fiber as a sub-category of rayon. Lyocell shares many properties with other cellulosic fibers such as cotton, linen, ramie and rayon. Some main characteristics of a lyocell fiber is that it is soft, absorbent, very strong when wet or dry, moisture wicking, anti-bacterial, and resistant to wrinkles. Lyocell can also be machine-washed, hand-washed, or dry-cleaned, it drapes well, and it can be dyed many colors, as well as simulating a variety of textures like suede, leather, or silk. See FiberSource (www.fibersource.com/f-tutor/lyocell.htm and www.tencel.at).
One known manufacture of lyocell fibers is the Lenzing Group of Austria. Lenzing markets their Lyocell fiber under the trademark Tencel®. However, Lyocell is not available from Lenzing Fibers in an FR fiber format. Because lyocell fibers are not inherently flame resistant, this means that non-FR Lyocell fibers are lyocell fibers that have not been treated with a flame retardant.
Flame resistant fibers, aka FR fibers, are those fibers that have flame resistance as an essential characteristic of the fiber. Flame resistant fibers could be inherently flame resistant fibers or fibers treated to become flame resistant. Typically, a treated fiber is a conventional textile fiber that has been treated with a flame retardant, a chemical substance used to impart flame resistance. Not only can the fiber be treated with a flame retardant, but the resulting fabric can also be treated with a flame retardant to make the fabric flame resistant. For example, treated fibers or fabrics include: FR cotton, FR treated Rayon (both FR cellulosics), and the like. Inherently flame resistant fibers may include, but are not limited to: aramids, polyamide imides, melamines, polybenzimidazole (PBI), polyimides, polyphenylene benzodisoxazole (PBO), polyphenylene sulfide (PPS), Polytetrafluoroethylene (PTFE), polyetherether ketone (PEEK), modacrylic, FR Rayon, glass, carbon, and the like. Most often, these flame resistant fibers (treated and/or inherent) are blended together to obtain a yarn for a fabric with a particular blend of properties. Those properties include thermal protection, break-open protection, static resistance, comfort, durability, stability, appearance, moisture management, abrasion resistance, anti-bacterial, ease of laundry maintenance, color, and relative cost.
One known flame resistant fabric that utilize the cost, comfort, absorbency, and durability of lyocell fibers, especially non-FR Lyocell Fibers, with the flame resistant properties of a flame resistant fiber, is disclosed in US Patent Publication No. 2008/0057807. This fabric requires an FR modacrylic (modacrylic is inherently flame resistant, i.e., the terms ‘FR modacrylic’ and merely ‘modacrylic’ can be used interchangeably) to be blended with the non-FR lyocell. Another known flame resistant fabric that utilizes lyocell fibers with the flame resistant properties of a flame resistant fiber is disclosed in US Patent Publication No. 2008/0124993. The fabric disclosed is 15-25% FR modacrylic fibers blended with 75-85% FR treated cellulose, like rayon or lyocell. Thus, the fabric disclosed in this publication, not only requires an FR modacrylic to be blended with the lyocell fiber to extinguish the flame, but it also requires the lyocell fiber to be treated with a flame retardant. These two patent publications show that, prior to the instant invention, it was believed that a lyocell fiber could not be blended with flame resistant fibers to create a protective garment, especially with lyocell fibers present at a significant portion of the fabric (i.e., greater than 5%, unless the flame resistant fiber included modacrylic or the resultant fabric was finished with an FR treatment.
The instant invention is designed to address this problem and provide for new fabrics that will meet new and emerging needs of the industry by providing a flame resistant fabric/yarn made from lyocell fibers that does not require the use of modacrylic or the need to finish the fabric with an FR treatment.